Need help with charging schedule for L16 interstate batteries

MauiSun
MauiSun Registered Users Posts: 7 ✭✭
First, thanks for any help, this site has been a godsend.

I just upgraded my battery bank from golf cart batteries to L16s, and I'm having trouble finding the correct charging and EQ voltages.
I read somewhere that L16s should be charged at a much higher voltage, with absorption at 61.2V and float at 54.6, both which seem a bit high.
I couldn't find anything on equalizing voltage. It also said absorption time should be at least 3 hours long.

I couldn't find any information from interstate, and trojan recommends completely different numbers for their L16s, with absorb at 57.6 and float at 52.8, and EQ at 61.92

These seems like drastically different numbers..... which ones do i go with? and how often should i schedule an equalization cycle with these batteries?

Thanks for any tips!


Comments

  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited August 2017 #2
    From what I understand, therefore not 100% sure, Interstate batteries are manufactured by US Battery, perhaps someone who knows for sure can verify. Here is the pdf. for US Battery, if nothing else, it's information.
    Edit. Johnson Controls may be the parent, manufacturer/owner of Interstate, or both? Who knows, major conglomerates are eating up everything, or so it seems.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • Marc Kurth
    Marc Kurth Solar Expert Posts: 1,142 ✭✭✭✭
    What does your battery dealer suggest?

    Marc
    I always have more questions than answers. That's the nature of life.
  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    You might find that time constraints with solar force the use of higher voltages than normal.   Check specific gravity (SG) to verify.

    I am available for custom hardware/firmware development

  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    Some interesting reading regarding L-16 batteries.

    From Home Power Magazine. 

    Battery management and
    maintenance are significant
    concerns in off-grid PV systems.
    Many of the user problems associated
    with these systems can be traced to
    improper treatment and
    misunderstanding of battery
    performance.
    Modern battery chargers use three charging stages—
    bulk, finish (absorption), and float. Bulk brings the
    batteries up to the high voltage regulation point; finish
    holds it at this high voltage regulation point based on
    time. In the absorption stage, the voltage is constant,
    and the current tapers off as the batteries are filled.
    Float trickle charges the battery to a lower, userdetermined
    voltage to keep it full.
    From my experience, the most common battery problem
    is undercharging, leading to sulfation, loss of storage
    capacity, and shortened service life. Sandia National
    Laboratories recently published “PV Hybrid Battery
    Tests on L-16 Batteries” (see Access). Their tests
    represent several years of systematic testing of a PVgenerator
    (hybrid) system.
    The Sandia report is very thorough. Four different
    brands of batteries were tested. They were all flooded,
    L-16 type batteries, the most common battery used in
    residential-scale RE systems. Tests were repeated so
    that the data represents good averages, and the
    conclusions are based on good data and methodology.
    The study has four conclusions:
    1. The finish voltage (sometimes called the absorption
    voltage) for a flooded lead-acid battery operating at
    12 VDC nominal should be about 15.3 volts (2.55 per
    cell) rather than the customary 14.4 volts.
    2. Finish charge time should be at least 3 hours and
    often longer.
    3. The maximum interval between finish charges should
    be about five days.
    4. Not all brands of L-16s are the same (though the
    report names no names).
    The general conclusions of the Sandia report are
    consistent with the number one problem experienced in
    off-grid PV systems—undercharged batteries. Richard
    Perez has for many years advocated higher finish
    voltages for PV-engine generator systems. As he says,
    “I like to run them hot.”
    Home Power technical editor Joe Schwartz adds some
    good advice regarding flooded lead-acid batteries:
    • Higher finish charge rates result in significantly more
    gassing and potential for hydrogen buildup. Before
    you crank up the finish voltage to 15.3 VDC (for a
    nominal 12 volt system), make sure that the battery
    containment is well ventilated. The use of powered
    battery vents is recommended.
    • Batteries charged to a high finish voltage produce a
    significant amount of waste heat. Depending on the
    type and location of the battery containment, in warm
    climates or seasons active ventilation may be required
    to keep battery temperature in check. Optimal
    operating temperature for lead-acid batteries is 78°F
    (25°C). Higher battery temperatures (90°F plus; 32°C)
    result in increased self-discharge. Temperatures over
    120°F (49°C) can damage lead-acid batteries.
    • Batteries charged to a high finish voltage consume a
    lot of water. Compared to charging at the traditional
    14.4 VDC finish voltage, the time period between
    battery watering can easily be cut in half. Automatic
    battery watering systems greatly simplify the process.
    • Use temperature compensation on all charge
    controllers and inverter/chargers.
    Finish Charging Is Inefficient
    There is one significant downside to the battery
    management strategy presented in the Sandia report.
    Due to battery charging characteristics, efficiency is
    very low during the finish charge phase. Very long
    engine generator run times were reported, sometimes
    from 6 to 20 hours. These long run times were required
    to completely refill the batteries to the manufacturers’
    stated ampere-hour capacity.
    The state of charge (SOC) of a battery is most
    accurately measured with a hydrometer, and is
    indicated as specific gravity (SG). Most RE users rely on
    amp-hour meters to provide convenient (although
    slightly less accurate) battery SOC information. During
    the Sandia tests, full batteries had a SG in the range of
    1.290. The long, engine generator run times needed to
    achieve this SG translate into dollars and pollution (both
    audio and atmospheric). Perhaps there is a “middle
    way” that preserves the lifetime of the batteries while
    reducing the time and cost of engine generator finish
    charging.
    Revisit the Assumptions
    The batteries tested at Sandia were discharged by 60
    percent of capacity (to 40% SOC) and then charged
    back to rated capacity. In these tests, the rated
    capacities were determined empirically, and in most
    cases were close to the manufacturer’s stated value (in
    the range of 350 AH for an L-16).
    These two points require comment. First, this depth of
    discharge is not typical of most well-designed, standalone
    PV systems. This point is clearly stated by the
    author of the study. Most stand-alone PV systems, by
    design, cycle batteries by about 25 percent daily, not 60
    percent.
    Second, the manufacturer’s rated battery capacity and
    the way it is determined should be understood. All
    manufacturers recharge batteries on the grid. Using the
    grid, they can finish charge the batteries for long periods
    (on the order of 8 to 12 hours), cramming maximum
    ampere-hours into them. For a manufacturer, this
    method makes sense because it results in greater AH
    capacity figures for their product.
    The long engine generator run times required by PV
    hybrid systems must mimic the finish charge conditions
    the manufacturers use to rate the battery’s capacity.
    Perhaps batteries should be rated based on their
    application. For instance, a battery used in a standby
    application (such as utility backup system with grid
    recharging) might specify a full charge SG of 1.290. The
    same battery used in an application that regularly
    cycles the batteries (such as a PV system with engine
    generator backup) might have a recommended SG of
    1.250 to be considered full.
    It is true that a battery with a SG of 1.290 holds more
    charge than the same battery with a SG of 1.250.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    I have US Battery L16s, and use 58.8v for absorb, which seems to work fine, with EQs every month or two. Actual voltage is higher as the bank is almost always under 25°C. I use end amps at~1% of capacity for absorb time.

    As the batteries age (currently in their 4th year) I expect I'll need to increase voltage and maybe end amps a bit.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter